1. Field of the Invention
The present invention relates to a multi-screen display apparatus having screens of a plurality of projection type video image display apparatuses arranged, and particularly relates to the one capable of suppressing non-uniformity of the brightness among the plurality of projection type video image display apparatuses.
2. Description of the Background Art
Examples of an apparatus that displays a video image on a large screen include a multi-screen display apparatus having screens of a plurality of projection type video image display apparatuses arranged. As a light source of the projection type video image display apparatus included in the multi-screen display apparatus, for example, a high-voltage discharge lamp or an LED (Light Emitting Diode) that is a semiconductor light emitting element is adopted. In some cases, however, due to a variation during a process of manufacturing these devices, the plurality of projection type video image display apparatuses may exhibit non-uniform brightnesses. Presence of such non-uniformity of the brightness causes a conspicuous difference in the brightness among the screens, which may spoil a sense of unity of the large screen.
Therefore, conventionally, after installation of the multi-screen display apparatus, the brightness has been adjusted such that the screens have the same brightness based on a visual observation, or non-uniformity of the brightness has been suppressed based on an adjustment value obtained by using a measuring instrument such as a luminance meter. Such a technique is disclosed in, for example, Japanese Patent No. 3287007.
However, in a case where an operator adjusts the brightness based on the visual observation or the measuring instrument after installation of the multi-screen display apparatus, much time is required for the measurement and the adjustment, and additionally, depending on an installation place or the number of screens, it may be difficult to make the adjustment based on the visual observation or the measuring instrument.
Moreover, the adjustment based on the visual observation may sometimes cause non-uniformity of the brightness of the large screen after the adjustment due to non-uniformity of the technique of the operator.
Furthermore, in a case where a brightness adjustment and a chromaticity correction are implemented by adjusting the level of a video signal, the level of a gradation expression in each projection type video image display apparatus of the multi-screen display apparatus after the adjustment may be impaired.
There has been also a problem that a chromaticity is not performed even if an output of a light source is adjusted by adjusting an LED activation current.